A rotary electric apparatus described in JP 5948061 B (Reference 1) is a rotary electric apparatus having an integral slot configuration in which the number of slots per every pole and per every phase is an integer. Further, the rotary electric apparatus described in Reference 1 includes a stator winding having a plurality of slot conductor groups, each of which is constituted by a plurality of slot conductors in the same phase. Further, the plurality of slot conductors of the slot conductor group are inserted into and pass through a predetermined number Ns of slots arranged continuously in a circumferential direction of a stator core so that the slots and the layers are adjacent to each other. Further, the predetermined number Ns is set to Ns=NSPP+NL when the number of slots per every pole and per every phase is NSPP and the number of layers is 2×NL. Accordingly, the invention described in Reference 1 tries to reduce noise of the rotary electric apparatus.
A three-phase alternating-current motor described in JP 2016-140202 A (Reference 2) is a three-phase alternating-current motor having a fractional slot configuration in which the number of slots per every pole and per every phase is not an integer. Further, in the three-phase alternating-current motor described in Reference 2, windings overlap and are disposed in three layers per slot. Further, the winding of the first layer is disposed so that the disposition of each winding of three phases of U phase, V phase, and W phase has rotational symmetry of ±120 degrees in terms of a mechanical angle. The winding of the second layer is disposed to be misaligned by L slots with respect to the disposition of the winding of the first layer. The winding of the third layer is disposed to be misaligned by L slots with respect to the disposition of the winding of the first layer in a reverse direction of the direction of the misalignment of the winding of the second layer. Accordingly, the invention described in Reference 2 aims to reduce torque ripple of the three-phase alternating-current motor.
“Practical Electric Apparatus Study”, Moriyasu Shoji (published by Morikita Co., Ltd., Jul. 25, 2000 (First edition, First printing), p. 72) (Non-Patent Reference 1) describes that an armature winding is normally made to be an oblique slot by one slot pitch when it is necessary to remove a slot harmonic voltage, and the same effect is achieved even in the case where the armature winding is made to be an oblique slot by 1/c of the slot pitch in the case of a fractional slot configuration in which the number of slots per every pole and per every phase is not an integer. Herein, c refers to a denominator portion when the number of slots per every pole and per every phase is expressed as a mixed fraction and a proper fraction portion of the mixed fraction is expressed by an irreducible fraction.
However, the invention described in Reference 1 may not be applied to a rotary electric apparatus having a fractional slot configuration in which the number of slots per every pole and per every phase is not an integer. Specifically, in the rotary electric apparatus having the fractional slot configuration, the predetermined number Ns is not an integer, so that it is impossible to regulate the disposition of the plurality of slot conductors.
The invention described in Reference 2 tries to reduce torque ripple and it is difficult to reduce noise and vibration of the three-phase alternating-current motor. Specifically, in the three-phase alternating-current motor described in Reference 2, a magnitude of magnetomotive force generated by the windings in which the directions of the currents in the same phase accommodated in two slots adjacent to each other in a rotation direction of a rotor are the same changes at a ratio of 4:3:3:4 in the direction of the rotation of the rotor, and this is repeated. Because of this, even when the winding of the third layer is misaligned by a predetermined slot in the direction of the rotation of the rotor, the magnetomotive force generated when the winding is electrically conducted becomes uneven at every pole of the magnetic poles of the rotor. As a result, vibromotive force of a lower-order spatial deformation mode is more likely to be generated as compared to the number of magnetic poles of the rotor. The stator has a unique number of vibrations corresponding to the spatial deformation mode, and as the spatial deformation mode has a lower order, the three-phase alternating-current motor has a resonance point of noise and vibration in which the unique number of vibrations corresponding to the spatial deformation mode of the stator coincides with the frequency of the vibromotive force of the spatial deformation mode of the corresponding low order in the lower number of rotation, so that countermeasures are necessary.
As described in Non-Patent Reference 1, in the rotary electric apparatus having the fractional slot configuration, torque ripple (including cogging torque) may be reduced by a skew amount of 1/c of the slot pitch, but it is difficult to reduce noise and vibration of the rotary electric apparatus. Specifically, in the rotary electric apparatus having the fractional slot configuration, equivalence of each pole collapses in the electromagnetic attractive force distribution generated between the stator and a mover, so that vibromotive force of a spatial deformation mode of an order obtained by dividing the number of magnetic poles of the mover by c is generated. That is, in the rotary electric apparatus having the fractional slot configuration, vibromotive force of the spatial deformation mode of a lower order is more likely to be generated as compared to the rotary electric apparatus having the integer slot configuration (c=1) in the case where the number of magnetic poles of the mover is the same. As described above, the stator has the unique number of vibrations corresponding to the spatial deformation mode. As the spatial deformation mode has the lower order, the rotary electric apparatus has a resonance point of noise and vibration in which the unique number of vibrations corresponding to the spatial deformation mode of the stator coincides with the frequency of the vibromotive force of the spatial deformation mode of the corresponding low order in the lower number of rotation, so that countermeasures are necessary.
Thus, a need exists for a rotary electric apparatus which is not susceptible to the drawback mentioned above.